Overdrive swap question

[Mike Richards]

Hi all, I was asking Fid some questions about swapping an Overdrive Tranny into my 1953 Henry J which started life a base model 4 cylinder 3 speed manual. I am collecting parts to put an Overdrive in, the axle on the car at the moment is the original which has 4.26 gears. Fid informed me that '51 4 cylinder models and later Overdrives had 4.55 gears. My question is what effect would it have on the car to attempt to run it with the 4.26 gears? Maybe it would not run well, anyone have ideas or have done this, or know of someone that did??

[FleetMaster]

I cannot speak to the specifics in a Henry J, but in other vehicles a less than 10% gearing change to the final drive ratio was NOT a big change.  4.26 to 4.55 is a 7% change.  Now with OD engaged a 4.26 becomes equivalent to a 3.11 final and the 4.55 becomes a 3.32.  The experienced people need to speak on this but i have always liked a final drive ratio around 3.20 for a torque strong engine on the highway and closer to 3.00 for an engine that is big for a car's weight or strong running at 2500-3000 RPMs.

[Mike Richards]

Thanks, also emailed with "corsairdelux" and while not optimum the 4.26 would work and somewhere down the road I can find a rear end with 4.55

[Corsairdeluxe]

Hot rodder's mantra
350-350-350

350 engine-turbo 350- 350 rear end

[Fid]

Let us know how it works.  You will know right away if it's good or not. It is quite apparent if you connect a 6 cyl without OD to the 41/9 - 45mph is all it'll do and it will be screamin'

[kaiserfrazerlibrary]

There should be no noticeable difference if using the 4.26/4.27:1 rear axle unless you are doing a lot of driving over very high hills or in the mountains (going up hill)

[Mike Richards]

Thanks to all the advice on this, I do intend to go through with the swap but will wait til I get all the parts, I'm learning and have to figure this out,  where I live in Upstate NY has a lot of hills (some people might even say mountains). I've got my home work to do and a lot of things to get done on the car. Thank You all for your help!

[r1lark]

Mike, my experience with Henry J's and the 4 cylinders in these cars is nil. But I do have a lot of experience with the Borg Warner O/D in Studebaker six cylinders and V8s. The Stude rear end ratios on a six cylinder without and with O/D are similar to the Henry J rear end ratios mentioned. With a Stude 6 cylinder (170 cu inch), my experience has been that changing a straight 3 speed to a 3 speed/OD will work with the original non-OD rear axle ratio on flat roads and smaller hills, but on longer/steeper hills the engine does not have enough torque to pull the effective final drive ratio of approx. 3.00:1 -- causing the car to have to come out of O/D a lot sooner on a hill. You end up going in and out of O/D which gets old pretty quick.

The only way you will really know is to try the O/D with the present rear end ratio and see how it does. It may be ok for the driving you do with the car, you never know. My 2 cents worth.......

[Mike Richards]

I still think that I'll do it but I'll wait til I get the proper gears for the rear. The hills here would probably defeat the purpose. Lots of things and it'll be a gradual process